New game, new luck, and now I’m with the Lenovo E540 and Ubuntu 14.04 (64 bit). In short: my best Linux laptop experience so far.
The e540 comes with preinstalled Windows 7 and up to a while ago one would destroy the laptop and several other models irreversibly when installing Linux .
1) boot up Windows and have the Lenovo update tools upgrade the BIOS.
3) reboot and disable secure boot in the BIOS, also disable optimize OS defaults.
4) reboot and run Ubuntu from the USB drive
Post installation setup
1) The most annoying thing can’t be fixed at all: my specimen suffers from the screen door effect
. Apparently that’s not model-specific but affects only certain production charges. I’ve had worse and don’t even notice it anymore after a week of working with the computer. Just to be clear: this is a hardware issue, affects Windows also and has nothing to do with Ubuntu.
2) Ubuntu asked to activate the Nvidia drivers, I said yes and rebooted. Noteworthy: the laptop has, just like my previous Asus a dual graphic system. I didn’t want to go into the dual setup this time and am using the Nvidia per default. A reboot later,
everything still peachy.
[Update 25.02.2015] keeps freezing like the Asus. The collective wisdom of the interwebs says it is a Linux problem with the nvidia optimus (dual graphics card) technology. Installed Bumblebee  and graphics works fine and fast for both the standard desktop and 3D applications.
3) A quite nice Lenovo feature is the variable charge levels which are intended to prolong battery life. This works nice in Windows but is not supported out of the box with Ubuntu. However there is tp-acpi-bat
 which provides command line tools for specifying minimum and maximum battery charge levels.
4) [Update 25.02.2015] Ubuntu 14.04.2 was released today, I tried a new installation and the touchpad works fine.
I couldn’t befriend the default touchpad behavior, but a really simple startup script using synaptics  fixed the issue for me:
5) [Update 25.02.2015] Suspect/Resume is not working unless USB 3 support is disabled in the BIOS 
The obligatory checklist:
[X] Integrated camera
[X] fn + screen brightness
[X] fn + volume
[X] Internal speakers
[X] Internal microphone
[X] External speakers
[X] External microphone
[ ] Suspend NOT working
[ ] Ethernet (haven’t tested yet)
 Lenovo Thinkpad T540p bricked booting linux
 How to create a bootable USBstick on Windows
 Screen door effect